The present invention relates to a novel process for preparing a polyalkylene oxide having allyl end-groups, more particularly to a process for cheaply and easily preparing the polyalkylene oxide having a comparatively high molecular weight.
There have been proposed various processes for preparing polyalkylene oxides of which all of the chain ends are hydroxyl group, and polyalkylene oxides of which one end-group is olefin group and another end-group is saturated alkyl group.
Also, processes for preparing polyalkylene oxides having olefin group of allyl type in all of the chain ends are disclosed in U.S. Pat. No. 3,408,321 to Bruce A. Ashby et al and U.S. Pat. No. 3,592,795 to Bruce A. Ashby et al. The polyalkylene oxide disclosed in U.S. Pat. No. 3,592,795 is prepared by reacting hydroxyl end-groups of polyalkylene oxide with allyl isocyanate, and the polyalkylene oxide disclosed in U.S. Pat. No. 3,408,321 is prepared by reacting hydroxyl end-groups of polyoxyalkylene with a polyfunctional isocyanate compound such as toluene diisocyanate to give a polyalkylene oxide having an isocyanate end-groups and further reacting the isocyanate end-group with allyl alcohol. The allyl end-group in these polymers is bonded to the polyalkylene oxide chain through a urethane bonding. In either case, polyalkylene oxide having hydroxyl end-groups is employed as a starting material, and the reaction between hydroxyl group and isocyanate group is applied. However, as is well known, isocyanate group is very active to water and an isocyanate compound generates carbon dioxide gas or causes a side reaction in the presence of water. Therefore, in such processes employing polyalkylene oxide having hydroxyl end-groups as a starting material, the polyalkylene oxide must be substantially dehydrated and purified and therefore expensive. Also, an isocyanate compound is an expensive starting material by itself and must be carefully handled since isocyanate group is a toxic functional group and harms a skin in contact therewith. Thus, the processes according to U.S. Pat. Nos. 3,408,321 and 3,592,795 have the disadvantages that the obtained polymer is expensive due to employing expensive starting materials and there must be taken attention in preparation since preparing steps and procedures are complicate.
There has been well known an industrial process for preparing polyalkylene oxide having hydroxyl end-groups by subjecting an alkylene oxide monomer to addition polymerization with employing potassium hydroxide as a catalyst. In this process, the polymerization is commonly carried out under a catalytic concentration of 0.3 to 1.0 % by mole of potassium hydroxide to the monomer and at high temperature, as 100.degree. to 160.degree.C. It is well known fact that the potassium hydroxide being a catalyst is for the most part bonded to the chain-end of the produced polyalkylene oxide in a form of alkoxide ( OK) in the polymer solution so obtained. It is possible to introduce allyl group to the chain-end by reacting this alkoxide end-group with a an allyl halide compound, but very difficult to introduce it to all of the chain ends. The polymerization of alkylene oxide by potassium hydroxide is not a complete living polymerization and large amount of polyalkylene oxide having hydroxyl end-group is by-produced due to the chain transfer reaction during the polymerization. Therefore, it is impossible to prepare polyalkylene oxide having allyl end-groups in all of the chain ends merely by treating such a polymer solution prepared under a usual polymerization condition with an allyl halide comound. Even in the best case, the allyl end-group is at most 60 % by mole of the total end-groups. That is to say, it is the present state that the direct preparation of polyalkylene oxide of which all of the chain ends are allyl group by an addition polymerization of alkylene oxide monomer is difficult.